1Caption: The Three Mile Island nuclear power plant near Middletown, Pennsylvania.2 When you hear the words "nuclear energy," what do you think of? Many people think of warheads, bombs, and other dangers. However, there are "good" uses for nuclear energy, also. Just what is nuclear energy, and how is it produced?3 Nuclear energy is one energy source that doesn't come directly from the sun. It comes from atoms. Atoms are all around us. All matter, whether solid, liquid, gas, or plasma is made up of atoms.4 The core of an atom is called a nucleus. It is made of some particles that are positively charged, and others that are neutral. Some atoms are radioactive. They naturally undergo a process called nuclear fission.